Intelligent therapy system with evaporation management

ABSTRACT

Dressings, systems, and methods are disclosed that, in some embodiments, relate to treating a tissue site. In one embodiment, a dressing may include a manifold, a retention pouch, a sealing member, and a conduit interface. The manifold may be adapted to distribute reduced pressure to the tissue site, and the retention pouch may be adapted to retain and manage fluid extracted from the tissue site. The sealing member may cover the retention pouch and the manifold to provide a sealed space with the tissue site. The conduit interface may be in fluid communication with the sealed space and an exterior surface of the sealing member. The dressing may be utilized with a therapy device operable to control reduced pressure in the dressing and fluid flow over the sealing member.

RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.15/494,042, filed Apr. 21, 2017, which is a continuation of U.S. patentapplication Ser. No. 13/954,658, filed Jul. 30, 2013, now U.S. Pat. No.9,662,427, which claims the benefit, under 35 USC § 119(e), of U.S.Provisional Patent Application Ser. No. 61/682,449, entitled“INTELLIGENT THERAPY SYSTEM WITH EVAPORATION MANAGEMENT,” filed 13 Aug.2012, which is incorporated herein by reference for all purposes.

BACKGROUND

The following description relates generally to medical wound caresystems, and more particularly, to absorbent dressings, systems, andmethods that utilize reduced pressure to treat a tissue site. Dependingon the medical circumstances, reduced pressure may be used for, amongother things, reduced-pressure therapy to encourage granulation at atissue site, draining fluids at a tissue site, closing a wound, reducingedema, promoting perfusion, or fluid management.

Common dressings, systems, and methods typically include tubing,external canisters, and other components for providing reduced-pressuretherapy. These components may be cumbersome for the patient, expensive,and prone to leaking and blockages. Further, the dressing and associatedcomponents may require a particular orientation and installation inorder for the patient to receive effective therapy.

Effective management of fluids extracted from a tissue site areimportant considerations for the patient to receive effective therapy. Aleak or blockage in the system can cause a reduction in theeffectiveness of the therapy or a complete loss of therapy. Such asituation can occur if too much fluid is present in the dressing.

Thus, improvements that enhance patient comfort and usability whilemaintaining or exceeding current treatment capabilities are desirable.Further, improvements in system monitoring capabilities during therapycan increase reliability by providing accurate information to a userregarding any unfavorable conditions that may require corrective action.

SUMMARY

Shortcomings with certain aspects of tissue treatment methods,dressings, and systems are addressed as shown and described in a varietyof illustrative, non-limiting embodiments herein.

According to a first illustrative, non-limiting embodiment, a system fortreating a tissue site on a patient includes a dressing and a therapydevice. The dressing includes a manifold, a retention pouch, a sealingmember, and conduit interface. The manifold is adapted to be positionedadjacent the tissue site and is comprised of a hydrophobic material thatis fluid permeable. The retention pouch is adapted to be positionedadjacent the manifold and adapted to retain fluid. The retention pouchincludes an expandable portion and a recess. The expandable portion isadapted to expand to retain fluid in the retention pouch, and the recessis adapted to substantially preclude expansion. The sealing member hasan exterior surface and is adapted to cover the retention pouch and themanifold to provide a sealed space between the tissue site and thesealing member. At least a portion of the sealing member is comprised ofa material that allows vapor to egress from the sealed space through thesealing member. The conduit interface is coupled to the sealing member.

The conduit interface of the first embodiment includes an evaporativeflow conduit, a variable pressure conduit, a reduced-pressure conduit,and a manifold pressure conduit. The evaporative flow conduit is influid communication with the exterior surface of the sealing member. Thevariable pressure conduit has an inlet in fluid communication with thesealed space. The inlet of the variable pressure conduit is positionedto be in a spaced relationship relative to the expandable portion of theretention pouch. The reduced-pressure conduit has an inlet in fluidcommunication with the sealed space. The inlet of the reduced-pressureconduit is positioned to be in a spaced relationship relative to therecess in the retention pouch. The manifold pressure conduit has aninlet in fluid communication with the manifold. The inlet of themanifold pressure conduit is positioned between the retention pouch andthe manifold.

The therapy device of the first embodiment includes a fluid flow source,a variable pressure sensor, a reduced-pressure source, a manifoldpressure sensor, and a controller. The fluid flow source is in fluidcommunication with the evaporative flow conduit. The variable pressuresensor is in fluid communication with the variable pressure conduit. Thereduced-pressure source is in fluid communication with thereduced-pressure conduit. The manifold pressure sensor is in fluidcommunication with the manifold pressure conduit. The controller isadapted to receive a variable pressure signal from the variable pressuresensor and a manifold pressure signal from the manifold pressure sensor.The controller is operable to provide a reduced pressure output from thereduced-pressure source when the manifold pressure signal is greaterthan a target reduced pressure. Further, the controller is operable toincrease a fluid flow rate from the fluid flow source in response to anincrease in a pressure differential between the variable pressure signaland the manifold pressure signal.

According to a second illustrative, non-limiting embodiment, a systemfor treating a tissue site on a patient includes a dressing and atherapy device. The dressing includes a manifold, a retention pouch, asealing member, and a conduit interface. The manifold has a first sideand a second side, the first side facing opposite the second side. Thefirst side of the manifold is adapted to be positioned adjacent thetissue site. The retention pouch is adapted to retain a fluid and to bepositioned adjacent the second side of the manifold. The retention pouchincludes an absorbent core encapsulated between a first permeable layerand a second permeable layer. Additionally, the retention pouch includesan expandable portion and a recess. The sealing member has an exteriorsurface and is adapted to cover the retention pouch and the manifold toprovide a sealed space between the sealing member and the tissue site.The conduit interface is coupled to the sealing member.

The conduit interface in the second embodiment includes an evaporativeflow conduit, a variable pressure conduit, a reduced-pressure conduit,and a manifold pressure conduit. The evaporative flow conduit is influid communication with the exterior surface of the sealing member. Thevariable pressure conduit has an inlet in fluid communication with thesealed space. The inlet of the variable pressure conduit issubstantially aligned with and separated from the expandable portion ofthe retention pouch. The reduced-pressure conduit has an inlet in fluidcommunication with the sealed space. The inlet of the reduced-pressureconduit is substantially aligned with and separated from the recess inthe retention pouch. The manifold pressure conduit has an inlet in fluidcommunication with the manifold. The inlet of the manifold pressureconduit is positioned between the retention pouch and the second side ofthe manifold.

The therapy device of the second embodiment includes a fluid flowsource, a variable pressure sensor, a reduced-pressure source, amanifold pressure sensor, and a controller. The fluid flow source is influid communication with the evaporative flow conduit. The variablepressure sensor is in fluid communication with the variable pressureconduit. The reduced-pressure source is in fluid communication with thereduced-pressure conduit. The manifold pressure sensor is in fluidcommunication with the manifold pressure conduit. The controller isadapted to receive a variable pressure signal from the variable pressuresensor and a manifold pressure signal from the manifold pressure sensor.The controller is operable to provide a reduced pressure output from thereduced-pressure source when the manifold pressure signal is greaterthan a target reduced pressure. Further, the controller is operable toincrease a fluid flow rate from the fluid flow source in response to anincrease in a pressure differential between the variable pressure signaland the manifold pressure signal.

According to a third illustrative, non-limiting embodiment, a dressingfor treating a tissue site on a patient includes a manifold, a retentionpouch, a sealing member, and a conduit interface. The manifold includesa fluid permeable, hydrophobic material. The manifold has a first sideand a second side. The first side of the manifold is adapted to bepositioned adjacent the tissue site. The retention pouch is adapted tobe positioned adjacent the second side of the manifold and to retain afluid. The retention pouch includes an expandable portion and a recess.The expandable portion is adapted to expand to retain the fluid, and therecess is adapted to substantially preclude expansion. The sealingmember has an exterior surface and is adapted to cover the retentionpouch and the manifold to provide a sealed space between the tissue siteand the sealing member. At least a portion of the sealing member iscomprised of a vapor-permeable material that allows vapor to egress fromthe sealed space through the sealing member. The conduit interface iscoupled to the sealing member.

The conduit interface of the third embodiment includes an evaporativeflow conduit, a variable pressure conduit, a reduced-pressure conduit,and a manifold pressure conduit. The evaporative flow conduit is influid communication with the exterior surface of the sealing member. Thevariable pressure conduit has an inlet in fluid communication with thesealed space. The inlet of the variable pressure conduit is positionedto be in a spaced relationship relative to the expandable portion of theretention pouch. The reduced-pressure conduit has an inlet in fluidcommunication with the sealed space. The inlet of the reduced-pressureconduit is positioned to be in a spaced relationship relative to therecess in the retention pouch. The manifold pressure conduit has aninlet in fluid communication with the manifold. The inlet of themanifold pressure conduit is positioned between the retention pouch andthe manifold.

According to a fourth illustrative, non-limiting embodiment, a method oftreating a tissue site on a patient includes the steps of positioning amanifold over the tissue site, and positioning a retention pouch adaptedto retain a fluid over the manifold. The retention pouch includes anexpandable portion and a recess. When the retention pouch retains afluid, the expandable portion is adapted to increase in size and therecess is adapted to remain a substantially constant size. The methodadditionally includes the step of covering the retention pouch and themanifold with a sealing member to provide a sealed space between thetissue site and the sealing member. The sealing member has an exteriorsurface, and at least a portion of the sealing member is comprised of avapor-permeable material that allows vapor to egress from the sealedspace. Further, the method includes the steps of providing areduced-pressure conduit in fluid communication with the sealed space,and providing a variable pressure conduit in fluid communication withthe sealed space. The reduced-pressure conduit has an inlet positionedin a spaced relationship relative to the recess in the retention pouch.The variable pressure conduit has an inlet positioned in a spacedrelationship relative to the expandable portion of the retention pouch.Further, the method includes the step of measuring a manifold pressurebetween the manifold and the retention pouch. The manifold pressurecorresponds to a reduced pressure at the tissue site. Further, themethod includes the step of applying reduced pressure to the sealedspace through the reduced-pressure conduit until the manifold pressurereaches a target reduced pressure. The application of reduced pressureto the sealed space extracts fluid from the tissue site. The expandableportion of the retention pouch expands to retain the extracted fluid.Further, the method includes the step of measuring a variable pressurebetween the expandable portion of the retention pouch and the sealingmember at the inlet of the variable pressure conduit. Further, themethod includes the steps of calculating a differential pressure betweenthe manifold pressure and the variable pressure, and providing a fluidflow over the exterior surface of the sealing member. The differentialpressure corresponds to the amount of fluid retained by the retentionpouch. The fluid flow has a flow rate substantially corresponding to thedifferential pressure. The fluid flow over the sealing member evaporatesthe fluid extracted from the tissue site.

Other features and advantages of the illustrative embodiments willbecome apparent with reference to the drawings and detailed descriptionthat follow.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of this specification may be obtained byreference to the following detailed description when taken inconjunction with the accompanying drawings wherein:

FIG. 1 is a schematic of an illustrative embodiment of a system fortreating a tissue site on a patient;

FIG. 2 is a cut-away view of an illustrative embodiment of a dressingdepicted in FIG. 1;

FIG. 3 is a cut-away view of an another illustrative embodiment of adressing;

FIG. 4 is a side view of an illustrative embodiment of a conduitinterface depicted in FIGS. 1-3;

FIG. 5 is a top view of the conduit interface depicted in FIG. 4;

FIG. 6 provides a chart illustrating a plot of differential pressureversus time, and a flow rate corresponding to the differential pressure;and

FIG. 7 is a schematic of an another illustrative embodiment of a systemfor treating a tissue site on a patient.

DETAILED DESCRIPTION

In the following detailed description of non-limiting, illustrativeembodiments, reference is made to the accompanying drawings that form apart hereof. Other embodiments may be utilized, and logical, structural,mechanical, electrical, and chemical changes may be made withoutdeparting from the scope of this specification. To avoid detail notnecessary to enable those skilled in the art to practice the embodimentsdescribed herein, the description may omit certain information known tothose skilled in the art. Thus, the following detailed description isprovided without limitation and with the scope of the illustrativeembodiments being defined by the appended claims.

Referring to the drawings, FIG. 1 depicts an illustrative embodiment ofa treatment system 100 for treating a tissue site 102 on a patient 101.The tissue site 102 may be, for example, a wound, such as an open woundshown in FIG. 2, or an incision as shown in FIG. 3. The tissue site 102may extend through or otherwise involve an epidermis 106, a dermis 108,and a subcutaneous tissue 110. The treatment system 100 may also be usedat other tissue sites without limitation. Further, the tissue site 102may be the bodily tissue of any human, animal, or other organism,including bone tissue, adipose tissue, muscle tissue, dermal tissue,vascular tissue, connective tissue, cartilage, tendons, ligaments, orany other tissue. The treatment of tissue site 102 may include removalof fluids, such as exudate or ascites.

The treatment system 100 may include a dressing 112 and a therapy device113. A fluid communication conduit 115 may provide fluid communicationbetween the dressing 112 and the therapy device 113. The therapy device113 may apply internal reduced pressure and an external fluid flow tothe dressing 112 through the fluid communication conduit 115 fortreating the tissue site 102 as will be described further below.Further, the therapy device 113 may control the application of reducedpressure and fluid flow according to pressure feedback signals receivedfrom the dressing 112 through the fluid communication conduit 115.

Referring now to FIGS. 1-5, in one embodiment, the dressing 112 mayinclude a manifold 114, a retention pouch 116, a sealing member 118, anda conduit interface 119. The manifold 114 may have a first side 120, asecond side 122, and edges 123. The first side 120 and the second side122 may terminate at edges 123 and face in opposite directions from oneanother. The first side 120 of the manifold 114 may be adapted to faceinward toward the tissue site 102. The manifold 114 may include aplurality of flexibility notches or recesses (not shown) that may belateral cuts in the manifold 114. The manifold 114 may include one ormore longitudinal cuts or other cuts. The flexibility notches mayenhance the flexibility of the manifold 114. The enhanced flexibilitymay be particularly useful when the dressing 112 is applied over a jointor other area of movement. The manifold 114 may also be referred to as adressing bolster.

The manifold 114 may be formed from any manifold material or flexiblebolster material that provides a vacuum space, or treatment space, suchas, for example, a porous and permeable foam or foam-like material, amember formed with pathways, a graft, a gauze, or other similarmaterial. As a more specific, non-limiting example, the manifold 114 maybe a reticulated, open-cell polyurethane or polyether foam that providesgood permeability of fluids while under a reduced pressure. One suchfoam material is VAC® GranuFoam® material available from KineticConcepts, Inc. (KCl) of San Antonio, Tex. Any material or combination ofmaterials may be used as a manifold material for the manifold 114provided that the manifold material is operable to distribute reducedpressure. The term “manifold” as used herein generally refers to asubstance or structure that is provided to assist in applying reducedpressure to, delivering fluids to, or removing fluids from a tissuesite. A manifold may include a plurality of flow channels or pathways.The plurality of flow channels may be interconnected to improvedistribution of fluids provided to and removed from the area of tissuearound the manifold. Further examples of manifolds may include, withoutlimitation, devices that have structural elements arranged to form flowchannels, cellular foam, such as open-cell foam, porous tissuecollections, and liquids, gels, and foams that include or cure toinclude flow channels.

A material with a higher or lower density, or different pore size, thanGranuFoam® material may be desirable for the manifold 114 depending onthe application. Among the many possible materials, for example, thefollowing may be used: GranuFoam® material; Foamex® technical foam(www.foamex.com); molded bed of nails structures; patterned gridmaterial, such as those manufactured by Sercol Industrial Fabrics; 3Dtextiles, such as those manufactured by Baltex of Derby, U.K.; a gauze;a flexible channel-containing member; or a graft. In some instances itmay be desirable to add ionic silver to the foam in a micro bondingprocess, or to add other substances to the material, such asantimicrobial agents.

In one embodiment, the manifold 114 may be a hydrophobic layer. Thehydrophobic characteristics of the manifold 114 may prevent the manifold114 from directly absorbing fluid, such as exudate, from the tissue site102, but allow the fluid to pass through. Thus, as depicted by the fluidcommunication arrows 117 in FIGS. 2 and 3, the fluid may be drawn awayfrom the tissue site 102 as will be described below. Further, uponapplication of reduced pressure, the porous foam-like nature of themanifold 114 as described above may permit the manifold 114 to contractand apply a compressive force capable of closing a wound, such as theincision illustrated in FIG. 3.

Referring to FIG. 3, in one embodiment, a comfort layer 124 may becoupled, for example, by a heat bond 125 or any other suitabletechnique, to the first side 120 of the manifold 114. The comfort layer124 may provide comfort to the patient 101 when the manifold 114 isplaced adjacent to the epidermis 106 of the patient 101. The comfortlayer 124 may be any material that helps prevent skin irritation anddiscomfort while allowing fluid transmission through the comfort layer124. As a non-limiting example, a woven elastic material or a polyesterknit textile substrate may be used. As another non-limiting example, anInterDry™ textile material from Milliken Chemical of Spartanburg, S.C.,may be used. The comfort layer 124 may include anti-microbialsubstances, such as silver.

As used herein, the term “coupled” includes coupling via a separateobject and direct coupling. The term “coupled” also encompasses two ormore components that are continuous with one another by virtue of eachof the components being formed from the same piece of material. Also,the term “coupled” may include chemical, such as via a chemical bond,mechanical, thermal, or electrical coupling. Fluid coupling means thatfluid may be in communication between the designated parts or locations.

Continuing with FIGS. 1-5, the retention pouch 116 may include a firstpermeable layer 126, a second permeable layer 127, and an absorbent core128. In one embodiment, the absorbent core 128 may be encapsulatedbetween the first permeable layer 126 and the second permeable layer127. The first permeable layer 126 may have edges 126 a,b securedrespectively to edges 127 a,b of the second permeable layer 127 aroundor otherwise encapsulating the absorbent core 128. The edges 126 a,b and127 a,b of the first and the second permeable layers 126, 127 may besecured to one another in any suitable manner, such as, for example bythe heat bond 125 described above.

The retention pouch 116 may be adapted to retain fluid, such as fluidextracted from the tissue site 102. The first permeable layer 126 andthe second permeable layer 127 may each have a fluid acquisition surface129 facing in an opposite direction from a wicking surface 130. Thewicking surfaces 130 of the first and second permeable layers 126, 127may each have a grain (not shown) oriented in a longitudinal directionalong the length of the dressing 112. The orientation of the grain ofthe wicking surfaces 130 may serve to wick fluid, such as fluidextracted from the tissue site 102, along the length of the dressing112. The wicking of fluid in this manner may enhance the ability of theretention pouch 116 to retain and manage fluid efficiently forpreventing clogs as will be described in further detail below.

The retention pouch 116 may additionally include a recess 131 and anexpandable portion 121. When the retention pouch 116 retains a fluid asdescribed above, the expandable portion 121 may be adapted to increasein size, and the recess 131 may be adapted to remain a substantiallyconstant size. For example, in one embodiment, the first and the secondpermeable layers 126, 127 may be coupled to one another in any suitablemanner, such as with the heat bond 125 described above, to provide therecess 131. Thus, the coupling of the first and the second permeablelayers 126, 127 to one another may substantially preclude expansion ofthe recess 131. However, the expandable portion 121 of the retentionpouch 116 may be free of restriction and capable of expanding toaccommodate fluid being retained in the retention pouch 116 and theabsorbent core 128. Further, in another embodiment, the expandableportion 121 may extend radially outward from the recess 131.Additionally, in yet another illustrative embodiment, the recess 131 maybe capable of receiving or otherwise accommodating a filter 133. Forexample, the filter 133 may be positioned in a gap 135 that may bedefined between the recess 131 and the sealing member 118, describedbelow. The recess 131 and the filter 133 may further enhance the abilityof the dressing 112 to resist clogging.

The first and the second permeable layers 126, 127 may be any materialexhibiting the fluid acquisition and wicking characteristics describedabove, such as, for example, Libeltex TDL2, manufactured by Libeltex.Further, the filter 133 may comprise, for example, any hydrophobicmaterial, and the filter 133 may have any suitable shape, such as a3-dimensional shape.

The absorbent core 128 may be any absorbent material for retainingliquids and may, for example, include one or more of the following:Luquafleece® material; BASF 402c; Technical Absorbents 2317 availablefrom Technical Absorbents (www.techabsorbents.com); sodium polyacrylatesuper absorbers; cellulosics (carboxy methyl cellulose and salts such assodium CMC); or alginates. The absorbent core 128 may allow fluids andexudate removed from the tissue site 102 to be stored within theretention pouch 116 rather than external to the dressing 112.

Similar to the manifold 114, the absorbent core 128 of the retentionpouch 116 may include a plurality of flexibility notches (not shown) orrecesses that may be lateral cuts in the absorbent core 128. Theabsorbent core 128 may include one or more longitudinal cuts or othercuts. The flexibility notches may enhance the flexibility of theretention pouch 116, and may thereby increase the ability of theretention pouch 116 to conform to, for example, the joint of a patient.Further, the enhanced flexibility may assist in preventing anyinterference with the ability of the manifold 114 to contract asdescribed above.

The retention pouch 116 may have a maximum fluid capacity. At themaximum fluid capacity of the retention pouch 116, fluid communicationthrough the retention pouch 116 may be substantially precluded. Theretention pouch 116 may have a maximum fluid capacity of any amount tosuit a particular application.

In one embodiment, the manifold 114 may be positioned between the tissuesite 102 and the retention pouch 116 with the first side 120 of themanifold 114 facing the tissue site 102. In this embodiment, the fluidacquisition surface 129 of the first permeable layer 126 may bepositioned proximate to and facing the second side 122 of the manifold114, and the fluid acquisition surface 129 of the second permeable layer127 may be positioned facing the absorbent core 128.

The sealing member 118 may provide a cover over the manifold 114, theretention pouch 116, and at least a portion of the epidermis 106 of thepatient 101. The sealing member 118 may be positioned over the manifold114 and the retention pouch 116, and may provide a sealed space 132between the sealing member 118 and the tissue site 102. The sealingmember 118 may have an exterior surface 134 exposed to ambient air.Further, a portion of the sealing member 118 may include a sealingmember aperture 137 to allow fluid communication between the therapydevice 113 and the sealed space 132, the retention pouch 116, themanifold 114, and the tissue site 102.

In one embodiment, the second permeable layer 127 of the retention pouch116 may face the sealing member 118. In this embodiment, the recess 131may be positioned on the second permeable layer 127 and facing thesealing member 118.

The sealing member 118 may be formed from any material that allows for afluid seal. “Fluid seal,” or “seal,” means a seal adequate to maintainreduced pressure at a desired site given the particular reduced pressuresource or system involved. The sealing member 118 may be sealed, forexample, against the epidermis 106 or against a gasket or drape by asealing apparatus, such as a pressure-sensitive adhesive. Further, thesealing apparatus may be, for example, an adhesive sealing tape, drapetape or strip, double-side drape tape, pressure-sensitive adhesive,paste, hydrocolloid, hydrogel, or other similar material. If a tape isused, the tape may be formed of the same material as the sealing member118 with a pre-applied, pressure-sensitive adhesive. Thepressure-sensitive adhesive may be applied on a patient-facing side ofthe sealing-member 118 or portion thereof. Before the sealing member 118is secured to the epidermis 106, removable strips covering thepressure-sensitive adhesive may be removed.

In one embodiment, at least a portion of the sealing member 118comprises a liquid-impervious material that allows moisture vapor toegress from the sealed space 132 through the sealing member 118 and tothe atmosphere. For example, the sealing member 118 may be formed from ahigh-moisture-vapor-transfer-rate material (high MVTR material) or adrape material that may be a flexible film. “Moisture Vapor TransmissionRate” or “MVTR” may represent the amount of moisture that can passthrough a material in a given period of time. Ahigh-moisture-vapor-transfer-rate material may have a moisture vaportransmission rate greater than about 300 g/m² per a 24 hour period, ormore specifically, greater than about 1000 g/m² per a 24 hour period.

The sealing member 118 may comprise, for example, one or more of thefollowing materials: hydrophilic polyurethane; cellulosics; hydrophilicpolyamides; an INSPIRE 2301 material from Expopack Advanced Coatings ofWrexham, United Kingdom; a thin, uncoated polymer drape; naturalrubbers; polyisoprene; styrene butadiene rubber; chloroprene rubber;polybutadiene; nitrile rubber; butyl rubber; ethylene propylene rubber;ethylene propylene diene monomer; chlorosulfonated polyethylene;polysulfide rubber; polyurethane (PU); EVA film; co-polyester;silicones; a silicone drape; a 3M Tegaderm® drape; a polyurethane (PU)drape such as one available from Avery Dennison Corporation of Pasadena,Calif.; polyether block polyamide copolymer (PEBAX), for example fromArkema, France; or other appropriate material. The sealing member 118may be a hybrid drape formed of a combination of the previouslydescribed materials and may have a lower silicone layer (not shown)having perforated regions of exposed acrylic adhesive for securing thesealing member 118 to the patient 101 as previously described.

The conduit interface 119 may be coupled to the sealing member 118 ofthe dressing 112. The conduit interface 119 may be in fluidcommunication with the exterior surface 134 of the sealing member 118.Further, the conduit interface 119 may be in fluid communication withthe sealed space 132 through the sealing member aperture 137 in thesealing member 118. The fluid communication conduit 115 may providefluid communication between the therapy device 113 and the conduitinterface 119.

The conduit interface 119 may include an evaporative flow conduit 150, avariable pressure conduit 154, a reduced-pressure conduit 158, and amanifold pressure conduit 162. The evaporative flow conduit 150 may bein fluid communication with the exterior surface 134 of the sealingmember 118. The conduit interface 119 may include an evaporative flowoutlet 166 in fluid communication with the evaporative flow conduit 150.In one embodiment, the evaporative flow outlet 166 may be positionedcircumferentially about the conduit interface 119 for providingcircumferential fluid flow about the conduit interface 119 and over theexterior surface 134 of the sealing member 118.

The conduit interface 119 may be formed from a medical-grade, softpolymer or other pliable material. As non-limiting examples, the conduitinterface 119 may be formed from polyurethane, polyethylene, polyvinylchloride (PVC), fluorosilicone, ethylene-propylene, or other similarmaterials. In one illustrative, non-limiting embodiment, conduitinterface 119 may be molded from DEHP-free PVC. The conduit interface119 may be formed in any suitable manner such as by molding, casting,machining, or extruding. Further, the conduit interface 119 may beformed as an integral unit or as individual components.

The variable pressure conduit 154 may have an inlet 170 in fluidcommunication with the sealed space 132. The inlet 170 of the variablepressure conduit 154 may be positioned in a spaced relationship relativeto the expandable portion 121 of the retention pouch 116. In oneembodiment, the inlet 170 of the variable pressure conduit 154 may besubstantially aligned over the expandable portion 121 and the secondpermeable layer 127 of the retention pouch 116. Further, the inlet 170of the variable pressure conduit 154 may be positioned between theretention pouch 116 and the sealing member 118.

The reduced-pressure conduit 158 may have an inlet 174 in fluidcommunication with the sealed space 132. The inlet 174 of thereduced-pressure conduit 158 may be positioned in a spaced relationshiprelative to the recess 131 in the retention pouch 116. The recess 131may provide the gap 135. The gap 135 may be between the inlet 174 of thereduced-pressure conduit 158 and the retention pouch 116. In oneembodiment, the inlet 174 of the reduced-pressure conduit 158 may besubstantially aligned over the recess 131 and the second permeable layer127 of the retention pouch 116. Further, the inlet 174 of thereduced-pressure conduit 158 may be positioned between the retentionpouch 116 and the sealing member 118.

The manifold pressure conduit 162 may have an inlet 176 in fluidcommunication with the manifold 114. The inlet 176 of the manifoldpressure conduit 162 may be positioned between the retention pouch 116and the manifold 114. In one embodiment, the inlet 176 of the manifoldpressure conduit 162 may be positioned adjacent to the second side 122of the manifold 114. The manifold pressure conduit 162 may also be influid communication with the tissue site 102, the sealed space 132, andthe components of the dressing 112 by virtue of the fluid permeabilityof the manifold 114.

In one embodiment, the conduit interface 119 may include a base 180coupled at the inlet 176 of the manifold pressure conduit 162. In thisembodiment, the manifold pressure conduit 162 may have a length 183between the base 180 and the exterior surface 134 of the sealing member118. For example, the length 183 may be a length that the manifoldpressure conduit 162 extends into the sealed space 132 of the dressing112 from the exterior surface 134 of the sealing member 118. Themanifold pressure conduit 162 may extend through a retention pouchaperture 185 disposed, for example, through the recess 131 in theretention pouch 116. Similarly, the manifold pressure conduit 162 mayextend through a filter aperture 187 disposed through the filter 133.The base 180 may extend laterally outward from the inlet 176 of themanifold pressure conduit 162 and underneath the retention pouch 116.The base 180 may carry the retention pouch 116 between the base 180 andthe sealing member 118 such that the expandable portion 121 of theretention pouch 116 extends laterally beyond the base 180. The length183 of the manifold pressure conduit 162 may be sized according to thethickness of the retention pouch 116. For example, the length 183 mayprovide space for the expandable portion 121 of the retention pouch 116to increase in size prior to contacting the inlet 170 of the variablepressure conduit 154, as described below. In one embodiment, the length183 may be about 2.5 times the thickness of the retention pouch 116.

In another embodiment, the conduit interface 119 may include a membranefilter (not shown) in fluid communication with the sealing memberaperture 137 for prevention of clogs and transmission of odors from thedressing 112 during therapy. The membrane filter may be, for example, ahydrophobic or oleophobic filter. Additionally, the membrane filter mayinclude a substance, such as, for example, charcoal for controllingodor. The membrane filter may be replaceable or formed integrally withthe conduit interface 119. In another embodiment, the membrane filtermay be positioned in any suitable location in fluid communicationbetween the dressing 112 and the therapy device 113.

The therapy device 113 may include a fluid flow source 184, a variablepressure sensor 188, a reduced-pressure source 192, a manifold pressuresensor 196, and a controller 200. The fluid flow source 184 may be influid communication with the evaporative flow conduit 150. The variablepressure sensor 188 may be in fluid communication with the variablepressure conduit 154. The reduced-pressure source 192 may be in fluidcommunication with the reduced-pressure conduit 158. The manifoldpressure sensor 196 may be in fluid communication with the manifoldpressure conduit 162. In one embodiment, the fluid communication conduit115 may include a plurality of fluid communication lumens 202 thatprovide fluid communication between each of the previously describedcomponents of the therapy device 113 and the conduit interface 119. Inanother embodiment, the fluid communication lumens 202 may be providedas individual components rather than as a part of the fluidcommunication conduit 115.

The fluid flow source 184 may provide fluid flow as a part of thetherapy device 113 in the treatment system 100. In one embodiment, thefluid flow source 184 may be a positive-pressure source 186 thatprovides a positive-pressure output to the evaporative flow conduit 150for supplying fluid flow from the therapy device 113 to the exteriorsurface 134 of the sealing member 118. The fluid flow may have avariable flow rate as will be discussed below. The fluid flow source 184may be any suitable device or source for providing fluid flow, such as,for example, a pump or blower.

In another embodiment, the fluid flow source 184 may be any source offluid flow over the exterior surface 134 of the sealing member 118. Forexample, the fluid flow source 184 may be ambient air directed over theexterior surface 134 of the sealing member 118. Further, the fluid flowsource 184 may be reduced pressure applied to the evaporative flowconduit 150 for drawing fluid across the exterior surface 134 of thesealing member 118 and back to the therapy device 113.

As a part of the therapy device 113 in the treatment system 100, thereduced-pressure source 192 may provide reduced pressure to the dressing112. In one embodiment, the reduced-pressure source 192 may provide areduced pressure output to the reduced-pressure conduit 158 for applyingreduced pressure to the sealed space 132, the retention pouch 116, themanifold 114, and the tissue site 102. The reduced-pressure source 192may be any suitable device for providing reduced pressure as describedherein, such as, for example, a vacuum pump, wall suction, or othersource.

As used herein, “reduced pressure” generally refers to a pressure lessthan the ambient pressure at the tissue site 102 being subjected totreatment. In one embodiment, the reduced pressure may be less than theatmospheric pressure. In another embodiment, the reduced pressure may beless than a hydrostatic pressure at a tissue site. Unless otherwiseindicated, values of pressure stated herein are gauge pressures. Whilethe amount and nature of reduced pressure applied to a tissue site mayvary according to the application, the reduced pressure may be betweenabout −5 mm Hg to about −500 mm Hg, and more specifically, between about−100 mm Hg to about −200 mm Hg.

The reduced pressure delivered may be constant or varied (patterned orrandom) and may be delivered continuously or intermittently. Althoughthe terms “vacuum” and “negative pressure” may be used to describe thepressure applied to a tissue site, the actual pressure applied to thetissue site may be more than the pressure normally associated with acomplete vacuum. Consistent with the use herein, an increase in reducedpressure or vacuum pressure may refer to a relative reduction inabsolute pressure. An increase in reduced pressure corresponds to areduction in pressure (more negative relative to ambient pressure) and adecrease in reduced pressure corresponds to an increase in pressure(less negative relative to ambient pressure).

The controller 200 may be a printed wire assembly (PWA) or anapplication specific integrated circuit (ASIC) or other control device.The controller 200 may be adapted to receive a variable pressure signalfrom the variable pressure sensor 188 and a manifold pressure signalfrom the manifold pressure sensor 196. Reduced pressure communicatedfrom the variable pressure conduit 154 to the variable pressure sensor188 may provide the variable pressure signal, and reduced pressurecommunicated from the manifold pressure conduit 162 to the manifoldpressure sensor 196 may provide the manifold pressure signal. Thecontroller 200 may receive the variable pressure signal and the manifoldpressure signal in any suitable manner, such as, for example, by wiredor wireless electronic communication.

The controller 200 may be operable to provide the reduced pressureoutput from the reduced-pressure source 192 when the manifold pressuresignal is greater than a target reduced pressure. For example, thereduced pressure output may be provided when the reduced pressurecorresponding to the manifold pressure signal is less negative relativeto ambient pressure than the target reduced pressure. Conversely, thecontroller 200 may cease or preclude the reduced pressure output fromthe reduced-pressure source 192 when the manifold pressure signal hasreached the target reduced pressure. Further, the controller 200 maycontrol the reduced pressure output from the reduced-pressure source 192to the dressing 112 when the manifold pressure signal falls within athreshold of the target reduced pressure. In this manner, the controller200 may be capable of maintaining the reduced pressure in the dressing112 at the target reduced pressure or within a threshold thereof. Thetarget reduced pressure may be any reduced pressure to suit a particularapplication for the dressing 112. For example, the target reducedpressure may be input by a user into a control panel (not shown) orother input device associated with the controller 200.

Further, the controller 200 may be operable to increase the flow ratefrom the fluid flow source 184 in response to an increase in a pressuredifferential between the variable pressure signal and the manifoldpressure signal. The controller 200 may also be operable to decrease theflow rate from the fluid flow source 184 in response to a decrease inthe pressure differential between the variable pressure signal and themanifold pressure signal. The pressure differential between the variablepressure signal and the manifold pressure signal is the differencebetween the variable pressure signal and the manifold pressure signal.As will be described in further detail below, an increase in thepressure differential may correspond to a pressure drop across theretention pouch 116. The pressure differential and the pressure drop maycorrespond to an increase in the amount of moisture in the dressing 112.Thus, the controller 200 may control the rate of evaporation of moistureretained in the dressing 112 by varying the flow rate of fluid acrossthe sealing member 118 according to the level of moisture in thedressing 112.

For example, in the embodiment depicted in FIG. 1, a pump 204 mayprovide both the fluid flow source 184 and the reduced-pressure source192. The pump 204 may have a pump outlet 208 and a pump inlet 212. Inthis embodiment, the pump outlet 208 may provide the positive-pressuresource 186 as the fluid flow source 184, and the pump inlet 212 mayprovide the reduced-pressure source 192. The pump outlet 208 may be influid communication with the evaporative flow conduit 150, and the pumpinlet 212 may be in fluid communication with the reduced-pressureconduit 158.

Continuing with the embodiment of FIG. 1, the therapy device 113 mayadditionally include a valve 216 in fluid communication between the pumpinlet 212 and the reduced-pressure conduit 158. The valve 216 may have avalve outlet 220, a valve inlet 224, and an ambient air inlet 228. Thevalve outlet 220 and the valve inlet 224 may be coupled in seriesbetween the pump inlet 212 and the reduced-pressure conduit 158 suchthat fluid communication between the pump inlet 212 and thereduced-pressure conduit 158 is provided through the valve 216. When thevalve 216 is open, the valve 216 may permit fluid communication betweenthe reduced-pressure source 192 at the pump inlet 212 and thereduced-pressure conduit 158. When the valve 216 is closed, the valve216 may preclude fluid communication between the reduced-pressure source192 at the pump inlet 212 and the reduced-pressure conduit 158. In oneembodiment, when the valve 216 is closed, the valve 216 may providefluid communication between the pump inlet 212 and the ambient airthrough the ambient air inlet 228.

Continuing with the embodiment of FIG. 1, the controller 200 may beoperable to vary a rotational rate of the pump 204 or the time periodthe pump 204 is on or off. Further, the controller 200 may be operableto simultaneously open and close the valve 216 while varying therotational rate and/or the time period the pump is on or off. Therotational rate of the pump 204 or the time period the pump is on or offmay correspond to the positive pressure output at the pump outlet 208and the reduced pressure output at the pump inlet 212. However, when thevalve 216 is open, the valve 216 may permit reduced pressure from thepump inlet 212 to reach the reduced-pressure conduit 158. When the valve216 is closed, the valve 216 may preclude reduced pressure from reachingthe reduced-pressure conduit 158. Thus, the controller 200 may beoperable to control the positive pressure output and the reducedpressure output independently utilizing valve 216. Further, in oneembodiment, when the valve 216 is closed, the valve 216 may permitambient air to reach the pump inlet 212 in order to facilitate thepositive pressure output from the pump outlet 208.

The controller 200 may, for example, be electrically coupled in anysuitable manner to a solenoid (not shown) operable to open and close thevalve 212. In this manner, the controller 200 may vary the voltageoutput to the solenoid such as, for example, by a binary output, PulseWidth Modulation (PWM), or other output. Further, the controller 200 maybe operable to vary the rotational rate of the pump 204 and/or the timethe pump 204 is on or off in any suitable manner, such as, for example,by the Pulse Width Modulation (PWM) discussed above. Using Pulse WidthModulation, the rotational rate of the pump 204, the time the pump 204is on or off, and/or the solenoid may be said to operate based on a dutycycle. An increase in the percentage of the duty cycle may correspond toan increase in the rotational rate of the pump 204 or an increase in theamount of time the pump 204 is on for a given time period. For example,at a 100% duty cycle, the pump 204 may be operating at a maximum outputor rotational rate. Similarly, an increase in the percentage of the dutycycle may correspond to an amount of time that the solenoid remains ineither an open or a closed state. For example, at a 100% duty cycle, thesolenoid may be remain in either an open or a closed state for an entiretime period.

In another embodiment, the fluid flow source 184 and thereduced-pressure source 192 may be separate devices individuallycontrolled by the controller 200. For example, the controller 200 may becoupled in any suitable manner to a first solenoid operated valve (notshown) and a second solenoid operated valve (not shown). The firstsolenoid operated valve may be positioned in fluid communication betweenthe dressing 112 and the fluid flow source 184. The second solenoidoperated valve may be positioned in fluid communication between thedressing 112 and the reduced-pressure source 192. The controller 200 maycontrol the flow rate through the first and second valves by, forexample, the Pulse Width Modulation (PWM) discussed above.

Continuing with FIGS. 1-5, in operation, the controller 200 may providereduced pressure from the reduced-pressure source 192 to thereduced-pressure conduit 158 until the manifold pressure signal reachesthe target reduced pressure. The controller 200 may monitor the manifoldpressure signal and provide reduced pressure accordingly to maintain thereduced pressure in the dressing 112 at the target reduced pressure, orwithin a threshold thereof. Further, the controller 200 may providefluid flow from the fluid flow source 184 to the evaporative flowconduit 150, thereby distributing the fluid flow across the exteriorsurface 134 of the sealing member 118.

As previously described, the manifold 114 and the retention pouch 116may be formed of permeable materials that act as a manifold forproviding fluid communication between the conduit interface 119 and thetissue site 102. Thus, the reduced pressure distributed to the tissuesite 102 by the manifold 114 may draw fluid away from the tissue site102 toward the retention pouch 116 where the fluid may be retained. Asdepicted by the fluid communication arrows 117 in FIGS. 2-3, thereduced-pressure conduit 158 in the conduit interface 119 may be influid communication with the edges 123 of the manifold 114 along thesides of the dressing 112. In this configuration, the dressing 112 maynot require fluid communication through the retention pouch 116 in orderfor reduced pressure applied to the dressing 112 through thereduced-pressure conduit 158 to reach the tissue site 102. Accordingly,when the retention pouch 116 has reached the maximum fluid capacity, thereduced-pressure conduit 158 remains in fluid communication with thetissue site 102 at least by virtue of the fluid communication with theedges 123 of the manifold 114. The fluid communication between thereduced-pressure conduit 158 and the edges 123 may permit the manifold114 to distribute reduced pressure to the tissue site 102 if, forexample, the retention pouch 116 becomes substantially saturated withfluid, or otherwise clogged. In such a configuration, the edges 123 ofthe manifold 114 may provide an independent fluid communication pathbetween the reduced-pressure conduit 158 and the tissue site 102.

As described above, the retention pouch 116 may include the first andthe second permeable layers 126, 127 that encapsulate the absorbent core128 for retaining fluid during treatment. As shown in FIGS. 2-3, thefirst permeable layer 126 may be positioned proximate the manifold 114,and the second permeable layer 127 may be positioned proximate thesealing member 118. The fluid acquisition surface 129 of the firstpermeable layer 126 may face the manifold 114, and the wicking surface130 of the first permeable layer 126 may face the absorbent core 128.The fluid acquisition surface 129 of the second permeable layer 127 mayface the absorbent core 128, and the wicking surface 130 of the secondpermeable layer 127 may face the sealing member 118.

As fluid contacts the first and the second permeable layers 126, 127,the fluid may be distributed by each of the wicking surfaces 130 alongthe length of the dressing 112. The grain of each of the wickingsurfaces 130 may be oriented along the length of the dressing 112 suchthat the fluid will follow the direction of the grain by a wickingaction without regard to the physical orientation of the dressing 112 atthe tissue site 102. As such, the fluid may be distributed and absorbedby the absorbent core 128 in a substantially even manner.

The configuration of the first and the second permeable layers 126, 127may be particularly useful in managing fluid extracted from the tissuesite 102 within the dressing 112. In one embodiment, as fluid contactsthe fluid acquisition surface 129 of the first permeable layer 126, thefluid may first be drawn into the retention pouch 116 and away from themanifold 114. Subsequently, the fluid may be wicked along the wickingsurface 130 of the first permeable layer 126 for absorption by theabsorbent core 128. As fluid contacts the wicking surface 130 of thesecond permeable layer 127, the fluid may be first wicked along thewicking surface 130 of the second permeable layer 127, away from thesealing member aperture 137. Fluid contacting the second permeable layer127 may first be wicked away from the sealing member aperture 137 topreclude clogging of the reduced-pressure conduit 158 near the sealingmember aperture 137. Clogging can occur, for example, from excess fluidnear the sealing member aperture 137. Subsequently, the fluid may bedrawn into the retention pouch 116 through the second permeable layer127 and absorbed by the absorbent core 128. Thus, the configuration andpositioning of the first and the second permeable layers 126, 127relative to one another may direct fluid away from the tissue site 102and away from the sealing member aperture 137 for storage in theretention pouch 116. In this manner, the tissue site 102 may be keptsubstantially free of fluids, and the reduced-pressure conduit 158, maybe kept substantially free of clogs.

The recess 131 on the retention pouch 116 may further enhance theability of the dressing 112 to resist clogging. For example, the recess131 may provide the gap 135 between the inlet 174 of thereduced-pressure conduit 158 and the retention pouch 116 as previouslydescribed. The gap 135 may substantially preclude excess fluid frombecoming lodged between the sealing member 118 and the retention pouch116 near the reduced-pressure conduit 158. As an additional precaution,the filter 133 may be positioned in the gap 135 to further precludeexcess fluids from reaching the reduced-pressure conduit 158.

Continuing with the operation of the embodiments of FIGS. 1-5, thecontroller 200 may vary the fluid flow rate from the fluid flow source184 over the exterior surface 134 of the sealing member 118 according tothe amount of fluid retained in the dressing 112. As previouslydescribed, one embodiment of the sealing member 118 may comprise amaterial that has a high MVTR and is thus capable of allowing moisturevapor to egress from the sealed space 132 to the atmosphere through thesealing member 118. Providing fluid flow over the exterior surface 134of the sealing member 118 may enhance the egress of moisture vapor fromthe sealed space 132 through the sealing member 118. An increase in theflow rate of the fluid may correspond to an increase in the rate ofevaporation of moisture vapor from the sealed space 132.

The controller 200 may vary the fluid flow rate from the fluid flowsource 184 based on the previously described differential pressurebetween the manifold pressure signal and the variable pressure signal.As previously described, the manifold pressure signal may correspond tothe pressure measured at the inlet 176 of the manifold pressure conduit162. Due to the positioning of the inlet 176 between the retention pouch116 and the manifold 114, the manifold pressure signal may approximatethe reduced pressure at the tissue site 102 without regard to the levelof fluid saturation in the retention pouch 116. Further, as previouslydescribed, the variable pressure signal may corresponds to the pressuremeasured at the inlet 170 of the variable pressure conduit 154. Due atleast in part to the positioning and alignment of the inlet 170 with theexpandable portion 121 of the retention pouch 116, the variable pressuresignal may vary with increased fluid retention in the retention pouch116 and the dressing 112. Thus, the differential pressure may correspondto a pressure drop across the retention pouch 116, providing anindication of the level of fluid saturation in the retention pouch 116and the dressing 112. An increase in the differential pressure maycorrespond to an increase in the fluid saturation of the retention pouch116 and the dressing 112. Thus, the controller 200 may increase the flowrate from the fluid flow source 184 in response to an increase in thedifferential pressure to accelerate the evaporation of the fluid throughthe sealing member 118.

Initially, the manifold pressure signal, the variable pressure signal,and the reduced pressure applied to the dressing 112 through thereduced-pressure conduit 158 may closely approximate one another.However, as the fluid retained in the retention pouch 116 increases, thevariable pressure signal may increase in pressure. For example, thevariable pressure signal may become less negative relative to ambientpressure due, at least in part, to the pressure drop created by thefluid in the retention pouch 116. Further, as the fluid in the retentionpouch 116 increases, the expandable portion 121 of the retention pouch116 may increase in size to accommodate the fluid, causing theexpandable portion 121 to approach the inlet 170 of the variablepressure conduit 154. When the retention pouch 116 has reached themaximum fluid capacity, the expandable portion 121 of the retentionpouch 116 may contact the inlet 170 of the variable pressure conduit 154and preclude fluid communication between the sealed space 132 and thevariable pressure conduit 154. In such a scenario, the controller 200may provide maximum flow rate from the fluid flow source 184 toremediate the excess fluid. The controller 200 may reduce the flow ratefrom the fluid flow source 184 as the excess fluid is evaporated and thedifferential pressure begins to return to a steady state or normalcondition, with the variable pressure signal closely approximating themanifold pressure signal.

If the controller 200 cannot remediate the excess fluid within aparticular time frame, the controller 200 may provide an alarmindicating, for example, that the dressing 112 needs to be changed.Further, if the manifold pressure signal increases or becomes lessnegative relative to ambient pressure, the controller 200 may alsoprovide an alarm. Such a variation in the manifold pressure signal mayindicate that the manifold 114 has become saturated with fluid and thatthe tissue site 102 is no longer being provided effective therapy. Inone embodiment, the controller 200 may provide an alarm if the manifoldpressure signal increases above a threshold amount of the target reducedpressure, such as, for example, a threshold pressure that is about 50%greater than the target reduced pressure. In another embodiment, thecontroller 200 may provide an alarm after an elapse of a time periodinput by a user. The alarms provided by the controller 200 may havevarying degrees of priority set by a user. For example, a standard alarmmay be provided for conditions indicating that the dressing 112 may needto be changed, and a full alarm may be provided for conditionsindicating that the tissue site 102 may not be receiving effectivetreatment. This specification contemplates the use of any suitabledevices for providing user inputs and outputs, such as, for example,display panels, key pads, electronic chimes, and other such devices.

Referring to FIG. 6, a chart is provided that illustrates an exemplaryembodiment of the previously described evaporative control features ofthe treatment system 100. The chart includes the differential pressure(mm Hg) on the vertical axis and time (hours) on the horizontal axis.The plot line 189 on the chart depicts the differential pressure betweenthe manifold pressure signal and the variable pressure signal, or thepressure drop across the retention pouch 116, versus time. When thedifferential pressure is less than about 5 mm Hg, for example, thecontroller 200 may provide a 20% duty cycle output for the fluid flowsource 184. A differential pressure of less than about 5 mm Hg in thisexample may require a low evaporation rate, or a low flow rate from thefluid flow source 184, indicating a low or normal level of fluidsaturation in the retention pouch 116 and the dressing 112. When thedifferential pressure is between about 5 mm Hg to about 15 mm Hg, forexample, the controller 200 may provide a 60%-80% duty cycle output forthe fluid flow source 184. A 60%-80% duty cycle in this example mayrequire a medium evaporation rate, or a medium flow rate from the fluidflow source 184, indicating a medium level of fluid saturation in theretention pouch 116 and the dressing 112. When the differential pressureis greater than about 15 mm Hg, for example, the controller 200 mayprovide a 100% duty cycle output for the fluid flow source 184. A 100%duty cycle in this example may require a maximum evaporation rate, or amaximum flow rate from the fluid flow source 184, indicating that theretention pouch 116 and the dressing 112 are almost fully saturated withfluid. Thus, as the duty cycle increases in the above examples, the flowrate of fluid from the fluid flow source 184 increases, therebyincreasing the evaporation rate of the fluid in the retention pouch 116and the dressing 112. A differential pressure setting input by a userand corresponding to a desired duty cycle or flow rate may be used totrigger the evaporation rates described above.

The storage, management, and disposition of extracted fluids in thedressing 112 provides many benefits. The potential for clogging asdiscussed above may be reduced and the storage of fluids within thedressing 112 may eliminate the need for external storage components thatcould potentially leak or cause discomfort. Further, the reduction inthe number of components lowers the volume that must be maintained atreduced pressure, thereby increasing efficiency. Also, the dressing 112may be capable of managing fluids without regard to any particularphysical orientation of the dressing 112 at a tissue site. Additionally,the treatment system 100 employing the dressing 112 may be capable ofremediating excess fluids and providing valuable information to a userregarding the status of the therapy and the state of fluid saturation inthe dressing 112. Thus, the treatment system 100 and the dressing 112 atleast provide increased comfort, usability, efficiency, and confidencethat a patient is receiving effective treatment.

This specification additionally provides an illustrative embodiment of amethod of treating a tissue site 102 on a patient 101. Referring to thepreviously described embodiments of FIGS. 1-5, one embodiment of themethod may include the step of positioning the first side 120 of themanifold 114 over the tissue site 102. Further, the method may includethe steps of positioning the retention pouch 116 over the second side122 of the manifold 114, and positioning the sealing member 118 to coverthe retention pouch 116 and the manifold 114. The method may furtherinclude the step of sealingly securing the sealing member 118 to theportion of the epidermis 106 of the patient 101, as described above, toprovide the sealed space 132 between the tissue site 102 and the sealingmember 118. Additionally, the method may include the step of providingthe reduced-pressure conduit 158 in fluid communication with the sealedspace 132. As described above, the reduced-pressure conduit 158 may havean inlet 176 positioned in a spaced relationship relative to the recess131 in the retention pouch 116. The recess 131 may provide a gap 135between the inlet 176 of the reduced-pressure conduit 158 and the recess131. The method may include the step of providing a variable pressureconduit 154 in fluid communication with the sealed space 132. Asdescribed above, the variable pressure conduit 154 may have an inlet 170positioned in a spaced relationship relative to the expandable portion121 of the retention pouch 116. The method may further include the stepof measuring a manifold pressure between the manifold 114 and theretention pouch 116. The manifold pressure may correspond to a reducedpressure at the tissue site 102. The method may further include the stepof applying reduced pressure to the sealed space 132 through thereduced-pressure conduit 158 until the manifold pressure reaches atarget reduced pressure. The reduced pressure may extract fluid from thetissue site 102, and the expandable portion 121 of the retention pouch116 may expand to retain the fluid. The method may additionally providethe step of measuring a variable pressure between the expandable portion121 of the retention pouch 116 and the sealing member 118. The methodmay provide the steps of calculating a differential pressure between themanifold pressure and the variable pressure, and providing a fluid flowover the exterior surface 134 of the sealing member 118. Thedifferential pressure may correspond to the amount of fluid retained bythe retention pouch 116. The fluid flow may have a flow ratecorresponding to the differential pressure that evaporates the fluidextracted from the tissue site 102.

In one embodiment, the method may include the step of signaling a fullalarm if the manifold pressure is greater than a pressure thresholdafter the manifold pressure initially reaches the target reducedpressure. In another embodiment, the method may include the step ofsignaling a full alarm after an elapsed time setting input by a user.

In one embodiment, the step of providing a fluid flow over the exteriorsurface 134 of the sealing member 118 may include the steps of matchingthe differential pressure with a plurality of differential pressuresettings input by a user that correspond to a flow rate, and providingthe corresponding fluid flow rate over the exterior surface 134 of thesealing member 118. In another embodiment, at a maximum differentialpressure setting, the method includes signaling a full alarm.

In another embodiment, at a maximum differential pressure setting, themethod may include the step of comparing an amount of power available tothe treatment system 100 with an amount of power required to provide thecorresponding fluid flow rate over the sealing member 118 for a timeperiod set by a user. Further, the method may provide the step ofsignaling an alarm for a supplemental power source if the amount ofpower available to the treatment system 100 is less that the amount ofpower required to provide the corresponding fluid flow rate over thesealing member for the time period. Further, the method may provide thesteps of canceling the alarm for the supplemental power source if thesupplemental power source is provided, and signaling a full alarm if thesupplemental power source is not provided. Further, the method mayprovide the steps of reducing the fluid flow rate over the sealingmember 118 according to the differential pressure settings if thedifferential pressure is less than the maximum differential pressuresetting, and signaling a full alarm if the differential pressure isabove the maximum differential pressure setting for an elapsed timeinput by a user.

Referring to an another illustrative embodiment depicted in FIG. 7, thetreatment system 100 may include a visual indicator 232 for providing avisual indication of the differential pressure. The visual indicator 232may include a first port 236 and a second port 240. The first port 236may be fluidly coupled to the variable pressure conduit 154, and thesecond port 240 may be fluidly coupled to the manifold pressure conduit162.

In one embodiment, the visual indicator 232 may include a tube 246having a piston 250 disposed in the tube 246. The piston 250 may bebiased to one end of the tube 246 by a spring 256. The tube 246 mayadditionally include a transparent window 260 for providing a visualindication of the displacement of the piston 250 in the tube 246. Thetransparent window 260 may have a plurality of graduated indicators 264that indicate the differential pressure based upon the displacement ofthe piston 250 in the tube 246.

In operation, reduced pressure from the variable pressure conduit 154may be applied to the first port 236, and reduced pressure from themanifold pressure conduit 162 may be applied to the second port 240. Thedifferential pressure between the variable pressure conduit 154 and themanifold pressure conduit 162 may displace the piston 250 in the tube246. For example, if the reduced pressure at the first port 236 isgreater, or more negative relative to ambient pressure, than the reducedpressure at the second port 240, the piston 250 will be displaced in thetube 246 toward the first port 236. If equipped, the graduatedindicators 264 may indicate the differential pressure by thedisplacement of the piston 250 shown through the transparent window 260.

In another embodiment, the visual indicator 232 may include a sensingdevice such as, for example, a proportional valve, relief valve, orpressure switch (not shown) coupled to the tube 246. The sensing devicemay detect the displacement of the piston 250 in the tube 246 andgenerate a signal corresponding to the differential pressure that may beinput to the controller 200 and utilized in the evaporative controlroutine described above.

Although this specification discloses advantages in the context ofcertain illustrative, non-limiting embodiments, it should be understoodthat various changes, substitutions, permutations, and alterations canbe made without departing from the scope of the specification as definedby the appended claims Further, it will be appreciated that any featuredescribed in connection with any one embodiment may also be applicableto any other embodiment.

What is claimed is:
 1. A dressing for treating a tissue site,comprising: a manifold comprising a fluid permeable, hydrophobicmaterial and having a first side and a second side, the first sideadapted to be positioned adjacent the tissue site; a retention pouchadapted to be positioned adjacent the second side of the manifold and toretain a fluid, the retention pouch comprising an expandable portion anda recess, wherein the expandable portion expands to retain the fluid andthe recess is substantially precluded from expansion; a sealing memberhaving an exterior surface and adapted to cover the retention pouch andthe manifold to provide a sealed space between the tissue site and thesealing member, wherein a portion of the sealing member is comprised ofa vapor-permeable material; and a conduit interface coupled to thesealing member, the conduit interface comprising: an evaporative flowconduit in fluid communication with the exterior surface of the sealingmember, a variable pressure conduit having an inlet in fluidcommunication with the sealed space and positioned in a spacedrelationship relative to the expandable portion of the retention pouch,a reduced-pressure conduit having an inlet in fluid communication withthe sealed space and positioned in a spaced relationship relative to therecess in the retention pouch, and a manifold pressure conduit having aninlet in fluid communication with the manifold and positioned betweenthe retention pouch and the manifold.
 2. The dressing of claim 1,further comprising a filter positioned in a gap provided by the recess,wherein the gap is positioned between the inlet of the reduced-pressureconduit and the recess in the retention pouch.
 3. The dressing of claim1, wherein the inlet of the reduced-pressure conduit and the inlet ofthe variable pressure conduit are positioned between the retention pouchand the sealing member.
 4. The dressing of claim 1, wherein the inlet ofthe manifold pressure conduit is positioned adjacent to the manifold. 5.The dressing of claim 1, wherein the manifold and the retention pouchprovide fluid communication between the reduced-pressure conduit and thetissue site, and wherein when the retention pouch has reached a maximumfluid capacity, the reduced-pressure conduit is in fluid communicationwith the tissue site at least through an edge of the manifold.
 6. Thedressing of claim 1, wherein when the retention pouch has reached amaximum fluid capacity, the expandable portion of the retention pouchcontacts the inlet of the variable pressure conduit and substantiallyprecludes fluid communication between the sealed space and the variablepressure conduit.
 7. The dressing of claim 1, wherein the conduitinterface further comprises an evaporative flow outlet in fluidcommunication with the evaporative flow conduit, wherein the evaporativeflow outlet is positioned circumferentially about the conduit interface.8. The dressing of claim 1, wherein the conduit interface furthercomprises a base coupled at the inlet of the manifold pressure conduitand extending laterally therefrom, wherein the retention pouch iscarried between the base and the sealing member, and wherein theexpandable portion of the retention pouch extends laterally beyond thebase.
 9. A system for treating a tissue site, comprising: a conduitinterface configured to be coupled to a sealing member for forming asealed space at the tissue site, the conduit interface comprising: anevaporative flow conduit in fluid communication with an exterior surfaceof the sealing member; a variable pressure conduit having an inlet influid communication with the sealed space; a reduced-pressure conduithaving an inlet in fluid communication with the sealed space; a fluidflow source in fluid communication with the evaporative flow conduit andconfigured to provide positive pressure to the exterior surface of thesealing member through the evaporative flow conduit; a variable pressuresensor in fluid communication with the variable pressure conduit; and areduced-pressure source in fluid communication with the reduced-pressureconduit and configured to provide reduced-pressure to the sealed spacethrough the reduced-pressure conduit.
 10. The system of claim 9, furthercomprising a dressing that includes: a manifold adapted to be positionedadjacent the tissue site; and a retention pouch positioned adjacent themanifold and between the sealing member and the manifold, the sealingmember adapted to cover the retention pouch and the manifold to providethe sealed space, wherein the conduit interface includes a manifoldpressure conduit having an inlet in fluid communication with themanifold and positioned between the retention pouch and the manifold.11. The system of claim 10, further comprising a controller adapted toreceive a variable pressure signal from the variable pressure sensor anda manifold pressure signal from a manifold pressure sensor in fluidcommunication with the manifold pressure conduit, wherein the controlleris operable to increase a fluid flow rate from the fluid flow source inresponse to an increase in a pressure differential between the variablepressure signal and the manifold pressure signal.
 12. The system ofclaim 10, wherein the manifold comprises a hydrophobic material that isfluid permeable.
 13. The system of claim 10, wherein the inlet of thevariable pressure conduit is positioned in a spaced relationshiprelative to an expandable portion of the retention pouch, and whereinthe inlet of the reduced-pressure conduit is positioned in a spacedrelationship relative to a recess in the retention pouch.
 14. The systemof claim 10, further comprising a filter positioned in a gap provided bya recess, wherein the gap is positioned between the inlet of thereduced-pressure conduit and the recess in the retention pouch.
 15. Thesystem of claim 10, wherein the inlet of the reduced-pressure conduit ispositioned between the retention pouch and the sealing member.
 16. Thesystem of claim 10, wherein the inlet of the manifold pressure conduitis positioned adjacent to the manifold.
 17. The system of claim 10,wherein the manifold and the retention pouch provide fluid communicationbetween the reduced-pressure conduit and the tissue site, and whereinwhen the retention pouch has reached a maximum fluid capacity, thereduced-pressure conduit is in fluid communication with the tissue siteat least through an edge of the manifold.
 18. The system of claim 10,wherein when the retention pouch has reached a maximum fluid capacity,an expandable portion of the retention pouch is configured to contactthe inlet of the variable pressure conduit and to substantially precludefluid communication between the sealed space and the variable pressureconduit.
 19. The system of claim 10, wherein the conduit interfacefurther comprises a base coupled at the inlet of the manifold pressureconduit and extending laterally therefrom, wherein the retention pouchis carried between the base and the sealing member, and wherein anexpandable portion of the retention pouch extends laterally beyond thebase.
 20. The system of claim 9, wherein the fluid flow source isconfigured to be controlled to change an amount of positive pressureprovided to the exterior surface of the sealing member based on anamount of moisture in the sealed space.
 21. The system of claim 9,wherein a portion of the sealing member is comprised of a material thatallows vapor to egress from the sealed space through the sealing member.22. The system of claim 9, wherein the conduit interface furthercomprises an evaporative flow outlet in fluid communication with theevaporative flow conduit, wherein the evaporative flow outlet ispositioned circumferentially about the conduit interface.
 23. The systemof claim 9, wherein the reduced-pressure source and the fluid flowsource are a pump, the pump having a pump inlet and a pump outlet,wherein the pump inlet is in fluid communication with thereduced-pressure conduit and the pump outlet is in fluid communicationwith the evaporative flow conduit.
 24. The system of claim 23, furthercomprising a valve in fluid communication between the pump inlet and thereduced-pressure conduit, wherein a controller is operable to open andclose the valve, wherein when the valve is open, the pump inlet is influid communication with the reduced-pressure conduit, and wherein whenthe valve is closed, the valve substantially precludes fluidcommunication between the pump inlet and the reduced-pressure conduit.25. The system of claim 24, wherein when the valve is closed, the pumpinlet is in fluid communication with ambient air.
 26. A system fortreating a tissue site, comprising: a conduit interface configured to becoupled to a retention pouch that is adapted to retain a fluid and thatis positioned between a sealing member and a base, the conduit interfacecomprising: a variable pressure conduit having an inlet in fluidcommunication with a first side of the retention pouch; and a manifoldpressure conduit having an inlet in fluid communication with a secondside of the retention pouch, wherein the base is coupled at the inlet ofthe manifold pressure conduit and extends laterally from the inlet ofthe manifold pressure conduit, and wherein an expandable portion of theretention pouch extends laterally beyond the base.